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Growth Hormone vs. Testosterone: A Retrospective Based on the Latest Research
by Karlis Ullis, MD with Josh Shackman, MA

I was one of the first private practitioners in the country to dispense growth hormone as part of an overall anti-program hormone replacement program for adults that fit the criteria of the “Adult Onset Growth Hormone Deficiency Syndrome”. Like many other anti-aging physicians, I was extremely impressed by the initial research on growth hormone showing dramatic improvements in body composition, kidney function, skin, mood, well being, etc. I have been a member of the Growth Hormone Research Society for many years and have closely followed all the latest research on growth hormone and other adult hormone replacement therapies. As the number of studies on growth hormone as well as testosterone has piled up since I first began prescribing testosterone, I believe now is the time to look back at the research and see if growth hormone and testosterone have lived up to their promises.

It is well established in bodybuilding circles that testosterone is superior to growth hormone for gaining muscle. However, growth hormone still is enormously popular and generally has a better reputation than testosterone both in bodybuilding and in anti-aging circles. The general impression is that testosterone will make you big, but at the price of acne, puffiness, temper tantrums, prostate enlargement, and possibly “gyno”. Well it is acknowledged that growth hormone is not as anabolic as testosterone, people still think of growth hormone as a hormone that will make you lean and toned with almost no side effects. Growth hormone also has a reputation as being the “fountain of youth” among anti-aging enthusiasts, whereas testosterone is still considered somewhat dangerous. The purpose of this article is to see how the research on testosterone and growth hormone from the last few years has supported or disputed the public’s view of these two hormones.

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Which is Better for Body Composition?
New research has shed some light on the anabolic effects of growth hormone. Several studies in the past have shown an increase in lean body mass in subjects taking growth hormone. However, lean body mass does not necessarily mean muscle, but anything that is not fat and this includes water, organ tissue growth, bone mass, and connective tissue growth. My friend Michael Mooney (author of Built to Survive and editor of the Medibolics Newsletter) has helped publicize the fact that not much, if any, of the lean mass gained while on growth hormone is actually muscle. One recent study on HIV positive test subjects showed no significant change in skeletal muscle mass after taking six milligrams (about 18 units) per day of growth hormone for 12 weeks.(1) Another study, also on HIV positive test subjects, also showed a lack of muscle growth when doses of nine milligrams (roughly 27 units) per day were given.(2) Keep in mind that HIV positive individuals are often suffering from muscle wasting conditions, which should make them more responsive to any possible anabolic effects of growth hormone. Growth hormone is probably equally ineffective in healthy individuals.

One study on young (aged 22-33), highly trained athletes did show a significant increase in lean mass after six weeks of taking 2.67 milligrams (about 8 units) per day.(3) However this increase was only 4%, and may have not included any muscle mass at all. It seems overwhelming clear that growth hormone is either non-anabolic or very weakly anabolic for skeletal muscle when taken by itself, and it definitely not worth the large price if you are taking it solely for gaining muscle. The only real use in gaining muscle may be as a synergistic agent with testosterone. A synergistic effect of taking growth hormone with testosterone has been reported for increases in lean mass, but further research needs to be done to see if this synergistic effects holds for skeletal muscle. Keep in mind that some increases in lean mass are not desirable. Growing some organs too big such as kidneys can produce some embarrassing effects seen in some professional bodybuilders. You do not want your “guts” sticking blatantly out of your body.

But enough on growth hormone for muscle gain. For information, see Bryan Haycock’s article in this issue or go to Michael Mooney’s web site. If you are going to spend the money on growth hormone to try to improve your body, your best bet is to use it as a fat loss or “sculpting” agent. The previously mentioned study with growth hormone on trained athletes did show an impressive 12% decrease in bodyfat. So well it is well established that testosterone is far, far better for building muscle than growth hormone, is growth hormone the better choice for fat loss? The research on this issue is mixed, and there is no easy answer to this question.

One recent study put growth hormone head to head with testosterone and measured its effects on fat loss. In this study, men on growth hormone lost an average of 13% of their bodyfat compared to 5.8% in the group taking testosterone.(4) But before you jump to conclusions, there are a couple of reasons why this study doesn’t settle the question. For one thing, this study was on very old individuals (aged 65 to 88) who had low IGF-1 and testosterone levels. Another problem is that the doses of the hormones haven’t been reported yet (the study is only in abstract form right now) which also makes the comparison difficult to make. Most interesting about this study was that a synergistic effect was found in a group taking both testosterone and growth hormone, as they lost an average of 21% of their bodyfat. This is more than the averages of the testosterone alone and growth hormone alone groups combined.

Not all studies have shown this dramatic of an effect on body fat. One study using fairly large doses (adjusted by weight, but roughly 5 mg per day) on obese women failed to show any significant effects on body fat.(5) The growth hormone group lost less than two pounds more than the placebo group over a one month period. The main significant result was that the growth hormone group lost much less lean mass (an average loss of 1.52 kg compared to 3.79 in the placebo). While this may seem impressive, the same results could be achieved with a caffeine/ephedrine formula at a fraction of the price. While there are a good number of studies showing growth hormone to be effective for fat loss, testosterone may be almost as good for this purpose.

Testosterone was recently found to be effective for fat loss in young men even in small doses. One recent study showed that men given only 100 milligrams per week of testosterone enanthate lost an average of six percent of their bodyfat after eight weeks.(6) 100 mg per week is generally considered a very low dose by bodybuilding standards. Most impressive about this study was that the result was obtained in young, normal healthy men (aged 18 to 45), not obese or testosterone deficient. Most of the studies showing positive effects with hormone replacement therapy are on subjects who are obese or hormone deficient – i.e. the very subjects most likely to respond. While the amount of muscle gain reported in this study was not reported (it is still just in abstract form), another study showed 100 mg per week of testosterone enanthate was not anabolic.(7) It appears that testosterone has a strong mechanism for fat loss other than increased metabolic rate from increased muscle. Considering how much cheaper testosterone is than growth hormone, it may well be the cost-effective choice for burning fat even if it is slightly less effective overall.

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Safety of Growth Hormone and Testosterone
Testosterone is widely believed to be far more dangerous than growth hormone. However, recent research is rapidly showing that much of these dangers have been exaggerated. For instance, the hypothesis that testosterone causes prostate cancer has never been established. In fact, one study even showed a slight negative correlation between testosterone levels and prostate cancer! A study on young men given supraphysiologic doses of testosterone showed no change is prostate specific antigen (PSA), which is one measure of prostate cancer risk.(8)

Growth hormone may also be less dangerous to the prostate than previously believed. One study showed strong positive correlation with prostate cancer and IGF-1 levels.(9) Since growth hormone stimulates IGF-1 synthesis in the liver, this study and others bring up the possibility of a link of growth hormone and prostate and breast cancer. Keep in mind that statistical correlations do not necessarily prove causality, i.e. IGF-1 has not yet been proven to be a cancer-causing villain. Actually IGF-11 may be one of the culprits in the cancer story, and not IGF-1. At the Serano sponsored Symposia on the Endocrinology of Aging in October, 1999 and at the Endocrine Society Meeting in June, 1999 there was an informal consensus that patients on growth hormone did not increase their risk of breast or prostate cancer. Several other recent studies have also cast doubt on the role of growth hormone as a cancer-causing villain.

Testosterone may have also gotten a bad rap for its effects on blood lipids. Since testosterone and other anabolic steroids have been shown in some studies to lower HDL cholesterol levels, it was believed that testosterone may increase the risk for heart disease. This was refuted in one recent study on testosterone that showed some positive results. A study on 21 hypogonadal men (aged 36 to 57) showed a replacement dose of testosterone using the Androderm transdermal patch to reduce blood clotting.(9) While HDL levels did drop slightly, blood coagulability is believed to be the more important marker of heart disease risk. Another study showed a very strong negative correlation with testosterone levels and heart disease.

Growth hormone has shown mixed results on its effects on heart disease risk. One study on elderly men and women (aged 65-88) showed that growth hormone administration to lower LDL levels, but raised triglyceride levels.(10) Since high LDL and triglyceride levels are considered measures of heart disease risk, growth hormone’s effects on heart disease risk are ambiguous. However, long-term use of growth hormone as been shown to decrease the thickness of the carotid artery lining – i.e. increased room for blood flow.

While much more research needs to be done, I am convinced right now that testosterone replacement therapy in hypogonadal men may be safer than excessively large doses of growth hormone. The long-term studies have not yet been done to test the true long-term effects of these hormones, but the research seems quite clear at the moment. Michael Mooney has reported similar results on safety and side effects of these hormones:

While none of the studies on testosterone or anabolic steroids used for HIV have documented any significant health problems associated with their proper therapeutic use, Dr. Gabe Torres’ data on his patients who experienced a reduction in symptoms of HIV-related lipodystrophy with Serostim growth hormone showed that at the standard 5 and 6 mg doses, 80 percent of his HIV patients experienced significant side effects, that included elevated glucose, elevated pancreatic enzymes, or carpal tunnel syndrome. (1)

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Conclusion
Don’t get me wrong – I still use both growth hormone and testosterone as part of overall anti-aging programs in my patients. This article is not meant to say one hormone is “good” and another is “bad”. It is just my opinion at the moment that the overall benefit/cost ratio for improving body composition is higher with testosterone than growth hormone. By cost, I mean both the monetary price – testosterone is far cheaper than growth hormone, and the side effect/safety profile – testosterone is safer than high-dose growth hormone use.

Since growth hormone is extremely expensive and perhaps riskier than testosterone, I screen patients very carefully and only recommend it to those who either have very low IGF-1 levels and fail growth hormone stimulation tests, or those who have failed to respond to testosterone or other therapies. The new research has also made me confident in encouraging more and more patients to go on testosterone. However, we must keep constant track of the new research to better refine both anti-aging and bodybuilding programs. The science of hormone supplementation is still in its infancy, and there is still a lot more questions that need to be answered.